. >> reporter: he refused to release his tax returns, allowing another rival, newt gingrich, to take south carolina. >> we proved here in south carolina, that people power with the right ideas beats big money. >> reporter: but that big money eventually cleared the field. and romney set his sights on the president. >> it is still about the economy. and we arestupid. >> reporter: at number nine, bain. not that one. that one. almost as soon as romney had locked up the nomination, his former private investment firm, bain capital, was sacrificed by the super pacs, and the obama campaign. >> they sucked the life out of us. >> reporter: the attack ads put romney on the defense for months. >> there is nothing wrong with being associated with bain capital, of course. >> reporter: romney vowed to strike down the health care law himself. >> i am that one that is going to get rid of obama care. >> reporter: at number seven, gas. >> governor romney, do you feel the gas over shadowed the foreign trip? >> reporter: the candidate's missteps dominated. or in romney's case, the entire foreign trip, wh